Adjustable lap



R. G. ROSHONG ADJUSTABLE LAP May 20, 1952 Filed Feb. 26, 1949 W H H u /n n H INVENTOR. 8W M17 E9. 7 5M 2 W Patented May 20, 1952' UNITED STATES PATENT QFFl-CE ADJUSTABLE LAP Application February 26, 1949, Serial No. 78,602

4 Claims.

This invention relates to grinding and lapping machines, and particularly to a tool for lapping surfaces to any desired contour, from a flat to either a concave or convex form.

In lapping machines as commonly constituted, the tool is a circular plate made of cast material and having grooves, either circular or radial, for carrying away excess grit and lubricant. The working surface of the plate is generally flat, and if it is desired to lap a surface which is other than flat, another plate having the desired curvature is substituted for the flat plate. Thus it is necessary to purchase and maintain a-plurality of plates with each lapping machine if the machine is to be used to lap various forms of surfaces.

The principal object of this invention is to provide a tool for lapping surfaces, said tool being adapted to be used for forming convex, flat or concave surfaces.

Another object of this invention is to provide a tool for lapping surfaces, said tool being initially dished so as to form a convex surface, and means for distorting the tool to render the working surface of the tool either substantially flat or concave.

- These and other objects of this invention will become apparent from the following detailed description when taken together with the accompanying drawings, in which Fig. l is a side elevation of a lapping plate embodying the present invention;

Fig. 2 is a plan view of the lapping plate of Fig. 1;

Fig. 3 is a plan view of a modification of the plate of Fig. 1;

Fig. 4 is an enlarged side elevation in section of the plate of Fig. 1 showing the means for mounting it on a rotating platen;

Figs. 5 and 6 are views similar to Fig. 4, showing the plate in different conditions of operation; and

Fig. 7 is a side elevation of a further modification of the plate of Fig. 1 and the support therefor.

Referring now to the drawings for a detailed description of the invention, there is shown in Fig. 1 a circular plate It! having an upper working surface II and a lower working surface I2. The plate may be made of any desired material, but for purposes of illustration it will be described as cast iron of the grade commonly known as Meehanite. Both the upper and lower surfaces II and I2 are formed with grooves I3 and I4, respectively, which are disposed substantially radially with respect to surfaces II and I2 and also substantially perpendicularly with respect to the planes of the said surfaces I I and I2. The grooves I3 and I4 extend more than half-way through the plate and hence are staggered or out of register with one another so that grooves I4 are located midway between adjacent grooves I3. This results in a corrugated section. It is contemplated that in a lapping plate twelve inches in diameter the average thickness of the plate between grooves will be approximately and the axial thickness from the surface II to the bottom of a groove will likewise be A lapping plate so proportioned will have a slight amount of resilience, even though made of cast iron. It is this resilience which is relied upon to distort the lapping plate from a convex to a concave form. When the grooves I3, I4 are disposed radially on the plate, surface I I will be either conical or fiat, but will not be frustospherical. To approach more nearly a frustospherical contour, the grooves may be made circular as shown in Fig. 3. There the grooves I5 and I6 are made of substantially the same width as the grooves I3, I4, but are concentrically disposed about the center of the plate, thus forming circular pleats or corrugations. This disposition of the grooves permits the plate to assume a curved shape.

Referring now to Figs. 4, 5 and 6, the means by which different curvatures may be obtained in plate It will be described. It will be observed that plate I I) is mounted on a rotatable platen I'I having a centrally located drive shaft I8. The upper surface I9 is preferably made fiat. Plate Ill has a centrally located recess 20 which permits material being lapped to run out over the edge 2I of surface II, thereby avoiding the formation of ridges or shoulders on the said surface I I. The lapping plate II) is initially formed with a slightly dished shape so that surface I I is convex and the bottom surface I2 is concave. These shapes are shown greatly exaggerated in Figs. 4, 5 and 6, the actual deviation from flatness in a disc twelve inches in diameter being a few hundredths of an inch.

Lapping plate I0 has an opening 22 through which is passed a bolt 23 threaded into platen H. The depth of recess 20 is such that the head of bolt 23 does not protrude above surface II and hence it will not interfere with the work being lapped. The plate It is clamped to platen H by bolt 23 and the amount of curvature in the plate is controlled by bolt 23 also. Plate I0 is thinner at the center than at the outer periphery and is initially formed in such a manner that the variation from flatness of surface I2 is greater than the variation from flatness of surface ll. Thus the maximum convex curvature is obtained when bolt 23 merely holds plate Ill on platen l1. By tightening bolt 23 beyond this point, plate I is distorted to make surface ll flat as shown in Fig. 5, or to make surface I l' concave as shownin Fig. 6. In the last-mentioned figure, bottom surface 12 contacts upper surface is on platen l1 and thus determines the maximum concave curvature.

If the work to be lapped is to have a Hat surface, then plate [0 is adjusted as shown in Fig. 5, and surface I l is trued up with an appropriate truing tool before the work may be lapped. For a conical surface, the plate in is simply .distorted to the desired cone angle and is ready to be used (assuming that it was true when it was flat). For a convex or concave frustro-spherical surface, the plate: [0 is distorted to approximately the desired curvature and then a special truing tool, having the desired curvature, is used to perfect the surface. This procedure must be gone through each time the curvature is changed.

The form shown in Fig. '7 differs from the preceding forms in that the lapping plate 24 is initially formed with a substantially flat underside 25, the upper surface 25 being convex as before. Platen 27 has an annular bead 28' formed in the upper surface thereof, preferably at or near the outer edge of the platen. A bolt or screw 29 is utilized to hex the lap plate 24 from convex, through flat, to concave curvature as described with reference to the preceding forms.

It is obvious that with the Fig. 7 form, the desired effect can be obtained whether the head is continuous or not, as long as the edge of the lap plate 24 contacts the bead before the center of the said lap plate contacts the center of the platen 21. The surface of platen 2? within the head .28 .is therefore chosen to approximate the curvature of the underside 25 of lapping plate 24 and the-plate 24 is then distorted by moving its center toward the center of the platen 2'5.

The advantage of a distortable' lapping plate over a fixed plate resides in the versatility of the distortable plate. One such plate may take the place of many fixed plates. The desired curvature may be obtained in a shorter time than would be the case if one fixed lap were to be shaped solely by a truing tool from one curvature to. another.

It is understood that the foregoing description is illustrative of preferred embodiments of this invention and that the scope of the invention is not to be limited thereto, but is to be determined by the appended claims.

What is claimed is:

1. In a lapping machine, a lapping tool comprising in combination a circular platen mounted for rotation about a vertical axis, said platen having a raised upper peripheral surface, a circular lapping plate of appreciable thickness and formed of a material having limited flexibility centrally disposed on said platen, there being a circular weilformed in the upper surface of said plate the rim of which, in combination with the upper peripheral edge of the plate, defines a ring-like convex frusto-conical lapping surface, the lower peripheral edge of the plate resting upon .said peripheral surface of the platen and the medial regions of the underneath surface of the plate being spaced from the surface of the platen, there being a series of spaced radially disposed grooves formed in the upper surface of said plate and extending completely across said lapping surface and of a depth sufficient to lend added flexibility to the plate as a whole, there being a similar series of spaced radially disposed grooves formed in the lower surface of said plate and of a depth sufficient to lend further flexibility to the plate as a whole, the grooves in the upper and lower surfaces of the plate being circumferentially staggered on opposite sides of the plate, and adjustable clamping means extending axially and centrally through said plate and cooperating with the platen for drawing the central. regions of the plate toward the upper face of the platen to thus flex the plate and alter the contour of the lapping surface thereof from its original convex .frusto-conical shape, through a planar condition to a shape wherein it assumes a concave frusto-conical condition.

2. In a lapping machine, a lapping tool comprising, in combination a circular platen mounted for rotation about a vertical axis, said platen having a circular upper peripheral surface, a circular lapping plate formed of a material having limited flexibility and of appreciabl thickness centrally disposed on said platen, there being a circular well formed in the upper surface of said plate the rim of which, in combination with the upper peripheral edge of the plate, defines a ring-like convex frusto-conical lapping surface, the lower peripheral edge of said plate resting upon said peripheral surface of the platen and the medial regions of the'underneath surface of the plate being spaced from the upper surface of the platen, there being a series of spaced radially disposed grooves formed in the upper face .of the. plate and extending completely across said lapping surface and of a depth sufficient to lend added flexibility to the plate as .a whole, and adjustable clamping means extending axially and centrally through said plate and cooperating with the platen for drawing the central regions of the plate toward the upper surface. of the platen to thus flex the plate and alter the contour of the lapping surface thereof from its original convex frusto-conical shape, through a planar condition to a shape wherein it assumes a concave frusto-conical condition.

3. In a lapping machine, a lapping tool comprising in combination a circular platen mounted for rotation about a vertical axis, said platen having a circular upper peripheral surface, a circular lapping plate formed .of a material having appreciable thickness and formed of a material having limited flexibility centrally disposed upon said platen, there being a circularwell formed in the upper surface of said plate the rimof which, in combination with the upper peripheral edge of th plate, defines a ring-like lapping surface, the lower peripheral edge of said plate resting upon said peripheral surface of the platen and the medial regions of the underneath surface of the plate being spaced from the upper surface of the platen, there being a series of spaced radially disposed grooves formed in the upper surface of said plate and extending completely across said lapping surface and of a depth suflicient to lend further flexibility to the plate as a whole, there being a similar series of spaced radially disposed grooves formedin the lower surface of said plate and of a depth to lend further flexibility to the plate as a whole, the grooves in the upper and lower surfaces of the plate being circumferentially staggered on opposite sides of the plate, and a threaded member extending centrally through said plate and cooperating with the platen for drawing the central regions of the plate toward the upper face of the platen to thus flex the plate and alter the contour of the lapping surface.

4. In a lapping machine, a lapping tool comprising in combination a circular platen mounted for rotation about a vertical axis, said platen having a raised upper peripheral surface, a circular lapping plate formed of a material having limited flexibility and of appreciable thickness centrally disposed on said platen, there being a circular well formed in the upper surface of said plate the rim of which, in combination with the upper peripheral edge of the plate, defines a ring-like convex frusto-conical lapping surface, the lower peripheral edge of said plate resting upon said peripheral surface of the platen and the medial regions of the underneath surface of the plate being spaced from the surface of the platen, there being a series of concentric circular grooves formed in the upper surface of said plate and of a depth sufficient to lend added flexibility to the plate as a whole, and a threaded member extending axially and centrally through the bot- 6 tom of said recess and cooperating with the platen for drawing the central regions of the plate toward the upper face of the platen to thus flex the plate and alter the contour of the lapping surface thereof from its original convex frusto-conioal shape, through a planar condition to a shape wherein it assumes a concave frustoconical condition.

RAYMOND G. ROSI-IONG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 494,471 Gardner Mar. 28, 1893 1,058,940 Raybuck Mar. 25, 1913 1,641,791 Tone Sept. 6, 1927 1,815,104 Holt July 21, 1931 1,956,781 Waldron May 1, 1934 FOREIGN PATENTS Number Country Date 324,184 Germany Jan. 21, 1919 

